JP4698337B2 - Cantilevered excavator and cantilevered excavation method - Google Patents

Description

  The present invention relates to a cantilever excavation apparatus and a cantilever excavation method for excavating the ground in a non-open cut by a single push from the start side. In particular, this technology can be applied to laying various pipes such as a horizontal well pipe, a chemical solution injection pipe for recovering contaminated ground, a water and sewage pipe, a gas pipe, and a cable housing pipe for data communication on the ground.

  As a technique for freely excavating the ground by pushing the excavation tool from the starting side, and a technique for laying various pipes in the excavation hole, the cantilever excavation technique proposed by the present applicant is known ( Patent Document 1).

  This cantilever drilling technology has an inner tool with an inner bit attached to the tip of the inner pipe and an outer tool with an outer bit attached to the tip of the outer pipe. Realized by a tube-structured drilling tool.

  In the outer tool, the outer bit can freely rotate with respect to the outer tube, and the outer bit is rotated in conjunction with the inner tool by transmitting the rotational force directly applied to the inner tool to the outer tool. Further, the outer bit can advance and retreat in the axial direction with respect to the outer pipe, and the outer bit strikes in conjunction with the inner tool by transmitting the striking force directly applied to the inner tool to the outer bit. That is, the rotational force, striking force, and feed force on the starting side are directly applied to the inner tool and indirectly to the outer bit via the inner tool.

Therefore, during ground excavation, the outer tool is entrained by applying a pushing force only to the inner tool, and continuous excavation applied to the inner tool and stopping of continuous rotation and interlocking with the outer bit, while excavating difficult gravel layers and When encountering galley including construction waste, etc., it achieves excellent excavation performance that can continue to dig by hitting the inner tool and hitting the outer bit in conjunction with it.
JP 2004-232304 A

  However, since the conventional excavation tool has a double pipe structure over the entire length, it is difficult to bend, and it is difficult to sufficiently exhibit the curve propulsion that is the superiority of free excavation. Moreover, since the double-pipe structure is used over the entire length, the weight is heavy, and the propulsion resistance is considerably increased because the earth pressure is received during propulsion. Therefore, in order to realize sufficient excavation efficiency suitable for shortening the construction period with only one pushing propulsion force applied to the inner tool, and to effectively exert the striking force that breaks through gravel layers and galley that are difficult to excavate, the feeding force The use of large drilling propulsion devices with high striking power is unavoidable.

  The present invention has been made against the background of the prior art as described above. Its purpose is to realize a one-push free excavation technology that can fully demonstrate curved excavation, which is the superiority of free excavation, and the excavation efficiency of free excavation is high and encounters a difficult place without depending on the enlargement of the excavation propulsion device Even so, it is to realize a one-push free excavation technique that can sufficiently exhibit effective blow excavation.

  In order to achieve the above object, the present invention is configured as follows.

  One side pushable excavation device of the present invention includes a cylindrical rod portion in which a plurality of extension rods are connected, a cylindrical outer tool connected to the tip of the rod portion, and an outer bit attached to the tip, an outer tool, and a rod An inner tool that is substantially housed in the outer tool so that it can be inserted into and removed from the part, and an inner bit is attached to the tip of the inner part. A single-pushing propulsive force accompanied by at least any combination of hitting or hitting stop along the axial direction is transmitted to the outer tool only through the rod portion, and the ground is freely excavated.

  In the one-side pushable excavator of the present invention, the inner tool is substantially accommodated in the outer tool, and the excavation tool itself that realizes the one-push free excavation is not a double-pipe structure but is lightly equipped. Therefore, it is possible to solve various problems of the conventional excavation tool based on the difficulty of bending and the increase in propulsion resistance due to the weight load, while assuming that the propulsion is one-sided propulsion, free excavation (direction control), and possible to hit.

In other words, according to the present invention, the rod portion is light and has a single tube structure along the longitudinal direction. For this reason, it is easy to bend and can fully demonstrate curved excavation, which is an advantage of free excavation. The striking force that breaks through high gravel layers and glass can be fully demonstrated.
And, according to the present invention, the inner tool can be inserted into and removed from the outer tool and the rod part. And a pipe | tube can be laid in the ground by collect | recovering a rod part and an outer tool.

  The one-way pushable excavator is configured as an invention in which an inner tool is provided with a latch that can be engaged and disengaged with respect to an outer tool.

  According to the present invention, since the inner tool can be engaged with and disengaged from the outer tool by the latch, the inner tool is fixed by the engagement of the latch at the time of accommodation, and the inner tool is released by the engagement of the latch at the time of removal. And can be pulled out of the outer tool. In this case, the latch slides along the axial direction of the inner tool in conjunction with the engaging wing piece that can be opened and closed with respect to the axial direction of the inner tool, and the extraction of the inner tool from the outer tool. And a latch case that opens outward in the direction and closes the engagement wing piece that engages with the outer tool. In this case, the latch can be easily and automatically released by sliding the latch case by simply pulling out the inner tool.

  The one-sided pushable excavator is configured as an invention further including a collection linear body that can be inserted into the rod portion and the outer tool and can be connected to the inner tool.

  According to the present invention, the recovery linear body can be fed from the rod portion, and the inner tool can be easily recovered from the outer tool and the rod portion. In this case, the collection linear body may be configured as an overshot attached to the wire line and its tip, or configured as an overshot attached to the rod and its tip, or may be configured as a hollow or solid rod. it can. The form of connection can be realized by engagement, screwing or the like.

  The one-way pushable excavator is configured as an invention in which an inner tool is provided with a joint portion that can be bent in the axial direction.

  According to the present invention, the joint part bends according to the curved bending of the rod part, and the inner tool can be collected smoothly. In this case, one or more joint portions are provided.

  The one-sided pushable excavator is configured as an invention further comprising an excavation propulsion device that applies the one-sided pushing force to the rod portion. Thereby, the aforementioned one-pushing propulsive force can be exhibited.

  Further, the one-side pushable excavation method of the present invention that achieves the above object is an extension in which an inner tool having an inner bit at the tip is accommodated in an outer tool having an outer bit at the tip and connected to the rear end portion of the outer tool. The outer tool penetrates into the ground together with the inner tool through the rod, and one-way propulsion with a combination of continuous rotation or continuous rotation stop around the axis of the extension rod and striking or striking stop along the axial direction of the rod part. Force is applied to the outer tool and the inner tool only through the extension rod to freely excavate the ground.

  According to the cantilevered excavation method of the present invention, it is assumed that the cantilever propulsion, the free excavation (direction control), and the hitting are possible, and the conventional push-out excavation method based on the increase in propulsion resistance due to difficulty in bending and weight load. Can solve various problems of one-sided free excavation method.

  In other words, according to the present invention, the rod portion is light and has a single tube structure along the longitudinal direction. For this reason, it is easy to bend, it can fully demonstrate curved excavation, which is the superiority of free excavation, and the excavation efficiency is improved without depending on the enlargement of the excavation propulsion device due to the decrease in propulsion resistance, and the excavation difficulty is high The striking force that breaks through gravel layers and glass can be fully demonstrated.

  In the one-sided free excavation method, after free excavation of the ground, the recovery linear body is inserted from the starting end of the extension rod and connected to the rear end of the inner tool, and the recovery linear body is pulled back. It is configured as an invention for collecting the inner tool.

  By collecting the inner tool, a cavity communicating with the extension rod is formed in the outer tool. For example, the outer tool itself can be used as various pipes such as a cable housing pipe for data communication. The pipe can be laid using the outer tool as a guide.

  In the one-push free excavation method, after collecting the inner tool, the pipe is laid on the ground by interpolating the pipe from the opening side opening end of the extension rod and then pulling back the extension rod and collecting the extension rod and the outer tool. It is configured as an invention.

  According to this, various pipes such as a horizontal well pipe, a chemical solution injection pipe for recovering contaminated ground, a water and sewage pipe, a gas pipe, and a cable housing pipe for data communication can be laid on the ground.

  According to the cantilever excavation apparatus and the cantilever excavation method of the present invention, curved excavation, which is an advantage of free excavation, can be sufficiently exhibited. Further, even if the excavation propulsion device does not depend on an increase in size, it is possible to sufficiently perform effective hitting excavation even when encountering a gravel layer or galley having high excavation efficiency and high excavation difficulty.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a cantilever excavator and a cantilever excavation method according to the present invention will be described with reference to the drawings.

One-push free excavator (Figs. 1-6)

  The one-side pushable excavator includes a excavation tool 1 whose outline is shown in FIG. 1 and a rod portion 2 shown in FIG. The recovery rod 3 and overshot 4 (FIG. 5), which will be described later, and the excavation propulsion device 5 (FIG. 6) are also provided as components of the one-push-able excavator.

Excavation tool 1 : The excavation tool 1 is composed of a steel outer tool 6 (FIGS. 1 and 2) and an inner tool 7 (FIGS. 1 and 3).

Outer tool 6 : The outer tool 6 includes an outer bit 8, a coupling 9, a sonde case 10, and a reducer 11 that are connected in order from the front end side.

  The outer bit 8 is formed in a substantially cylindrical shape, and a super steel tip 12 is implanted on the tip side thereof, and an earth pressure receiving surface 13 inclined with respect to the axial direction is formed. On the inner surface of the outer bit 8, a front engagement receiving portion 14 is formed that the inner tool 7 abuts in the excavation direction and is prevented from being pulled out. Reference numeral 15 denotes an engaging groove that engages with the inner bit 7 and prevents the inner bit 7 from rotating inside the outer bit 8.

  The coupling 9 is formed in a substantially cylindrical shape, and a rear engagement receiving portion 16 is formed on the inner surface of the inner tool 7 so that the inner tool 7 abuts in the pull-back direction and is prevented from being pulled out.

  The sonde case 10 has a substantially cylindrical shape that accommodates the sonde 17 that sends the position information of the excavating tool 1 that propels the ground to the ground. Therefore, the sonde case 10 is made of hard resin or the like for facilitating the transmission signal of the sonde 17. A transmission part 18 is provided. The sonde case 10 is formed with a drilling fluid passage 19 penetrating the wall thickness along the longitudinal direction.

  The reducer 11 is formed in a substantially cylindrical shape, and the rod portion 2 is connected to the rear end thereof.

Inner tool 7 : The inner tool 7 includes an inner bit 20, a latch part 21, a joint part 22, and a sonde storage part 23 connected in order from the front to the rear. The inner tool 7 can be inserted into and removed from the outer tool 6 and the rod portion 2 described above.

  The inner bit 20 excavates the ground together with the outer bit 8 described above. Therefore, the super steel tip 12 is planted on the tip side, and the earth pressure receiving surface 24 is formed. The earth pressure receiving surface 24 has the same inclination angle as the earth pressure receiving surface 13 of the outer bit 8 and forms a flush surface. A plurality of engaging protrusions 25 are formed on the outer peripheral surface of the rear end portion of the inner bit 20 so as to be separated in the circumferential direction. The engagement protrusion 25 abuts in the excavation direction against the front engagement receiving portion 14 of the outer bit 8 and prevents the inner bit 20 from being removed. A groove formed between adjacent engaging projections 25 serves as a passage for the drilling fluid and communicates with a passage 26 formed in the inner bit 20. An injection port 27 is opened at the end of the passage 26. The drilling fluid is jetted obliquely forward from here.

  The latch portion 21 is necessary for the inner bit 20 to be engaged with and disengaged from the outer bit 8 (fixed by engagement and removed by disengagement). The latch portion 21 is provided with a shaft 28, and the leading end thereof is inserted into and connected to the rear end opening of the inner bit 20. Two engaging blades 29 are attached to the shaft 28 by a rotating support shaft 30. Therefore, the engagement blade piece 29 can be opened and closed so that it opens outward with respect to the shaft center of the shaft 28 and closes inward with respect to the shaft center, with the rotation support shaft 30 as the opening and closing shaft. . Each engagement wing piece 29 in the open state has its shoulder portion 29a engaged with the rear engagement receiving portion 16 of the coupling 9 described above. As a result, the inner bit 20 is prevented from retreating with respect to the outer bit 8 even when subjected to earth pressure during excavation. Further, each engagement blade piece 29 in the open state enters and engages with the engagement groove 15 formed in the inner peripheral surface of the rear end portion of the outer bit 8. As a result, the inner bit 20 is prevented from rotating relative to the outer bit 8. Note that the inner bit 20 can be prevented from rotating by providing an engaging portion corresponding to the engaging protrusion 25 of the inner bit 20 on the inner peripheral surface of the outer bit 8. However, a height is required for engagement to prevent rotation, and if an engagement portion corresponding to the engagement protrusion 25 is provided in the outer bit 8, the inner diameter of the outer tool 6 becomes small, and the outer tool 6 The tube that can be inserted is also reduced. Because of this inconvenience, in this embodiment, the engagement blade piece 29 is also used as a detent for the inner bit 20 and is engaged with the engagement groove 15 of the outer bit 8.

  Then, it is the spring 31 incorporated therein that elastically biases the engagement blade pieces 29 that are to close inward to open outward. It is a point-shaped actuating rod 32 that enters between the engagement blades 29 that are opened by the spring 31 and maintains the open state. The actuating rod 32 receives the guide of the guide inner surface 28b of the rear end portion 28a of the shaft 28, and is movable back and forth with respect to the shaft 28 (between the engaging blade pieces 29). Specifically, the rear end portion of the actuating rod 32 is fixed to the rear end portion of the latch case 33 that houses the shaft 28 and the engagement blade piece 29 fixed thereto. When the operating rod 32 is pushed into the shaft 28, the operating rod 32 enters between the engagement blade pieces 29 as shown in FIG. On the other hand, when the operating rod 32 is pulled back with respect to the shaft 28, the operating rod 32 moves backward with respect to the shaft 28 as shown in FIG. At the same time, the latch case 33 fixed to the operating rod 32 also moves backward. By this retreat, the opening edge 33a of the latch case 33 is pushed inward so as to close the engagement blade piece 29 in the open state. Thus, the closed state of the engagement blade piece 29 is fixed. A spring 34 is attached to the inside of the latch case 33, and the latch case 33 is normally positioned so that the engagement blade piece 29 shown in FIGS.

  The joint portion 22 is a universal joint that can be bent by a single rotation support shaft 35 so that the inner tool 7 can be bent in the longitudinal direction.

  In the sonde storage unit 23, the sonde 17 is stored inside the inner sonde case 36. 37 is a protective material for the sonde 17. A spear 38 is attached to the rear end of the innersonde case 36, and an overshot 4 used for collecting the inner tool 7 is connected to the engaging head 38a. Specifically, the connecting operation is as shown in FIG.

Overshot 4 : That is, the recovery rod 3 is connected to the rear end portion of the overshot 4. The rod part 2 extends on the starting side, and the overshot 4 and the wire line 3 are fed into the pipe from the open end. Then, the overshot 4 reaches the reducer 11 of the outer tool 5 as shown in FIG. When the overshot 4 is fed as it is, the spear 38 passes through the insertion hole 39a with a guide inclined surface of the case 39 and abuts against the latch piece 40 in the back. Due to the impact, the latch piece 40 is opened via the rotation support shaft 41 and engaged with the engaging head 38a of the spear 38 as shown in FIG. Then pull back the recovery rod 3 from the start side. By merely pulling back, the engagement blade piece 39 is closed by the above-described mechanism, and the engagement of the engagement blade piece 39 with the engagement groove 15 and the engagement with the rear side engagement receiving portion 16 of the shoulder portion 39a are released. Then, the inner tool 7 can be pulled out from the outer tool 6.

Rod part 2 : As shown in FIG. 2, the rod part 2 is constituted by connecting a plurality of extension rods 42 in the longitudinal direction according to the excavation length. Each extension rod 42 has a hollow cylindrical shape, and the inside serves as a passage for the drilling fluid. The drilling fluid passing here passes through the inside of the drilling tool 1 including the passage 19 of the sonde case 10 and is jetted obliquely forward from the injection port 27 through the passage 26 of the inner bit 20. Further, the extension rod 42 has a thin middle portion so that the extension rod 42 is easily bent during curve excavation.

Excavation propulsion device 5 : The excavation propulsion device 5 is a piece that includes a combination of at least one of continuous rotation or continuous rotation stop along the axis of the rod portion 2 and striking or striking stop along the axial direction of the rod portion 2. A pushing propulsive force is applied to the rod portion 2 and directly transmitted to the outer tool 6 and indirectly to the inner tool 7. For this reason, the excavation propulsion device 5 includes a feeding device including a rotation mechanism and a striking mechanism. A drilling fluid feed mechanism is also provided.

One-push free excavation method (Fig. 6)

  Next, the one-push free excavation method will be described. In the construction method of this embodiment showing an example, an example will be described in which a pipe is laid on the ground using the one-side pushable excavator having the above-described configuration.

One-sided free excavation : The inner tool 7 is inserted and fixed to the outer tool 6 on the starting side, and the extension rod 42 is connected to the outer tool 6. These are penetrated into the ground using the excavation propulsion device 5. In the straight excavation by the single push propulsion, the rod portion 2 having a plurality of extension rods 42 connected is continuously rotated so that the earth pressure receiving surfaces 13 and 24 of the outer bit 8 and the inner bit 20 are not fixed at a specific rotation angle. The curved excavation stops the rotation of the rod portion 2 and fixes the earth pressure receiving surfaces 13 and 24 at a specific rotation angle. Then, the inclined earth pressure receiving surfaces 13 and 24 continuously receive the earth pressure of the ground, and the propulsion direction changes to the injection direction of the drilling fluid. Curve digging is done by continuing this as it is.

  Since only the excavation tool 1 has a double structure and the rod portion 2 has a single tube structure and is lightly equipped, it is easy to bend during curved excavation, and can fully exhibit curved excavation, which is an advantage of free excavation. In addition to this, by reducing the propulsion resistance due to the weight reduction of the rod portion 2, the excavation efficiency of the universal excavation can be improved without depending on the enlargement of the excavation propulsion device.

  In the process of straight excavation and curvilinear excavation, when hitting a gravel containing gravel layers and construction waste with high excavation difficulty, the outer bit 8 and the inner bit 20 are hit through the rod portion 2. At this time, since the rod portion 2 is lightly equipped with a single pipe structure, a strong striking force can be provided by the outer bit 8 without depending on a high-power striking mechanism in the excavation propulsion device 5 due to a decrease in propulsion resistance due to its weight reduction. And can be generated in the inner bit 20. Therefore, it is possible to continue digging through the difficult place without pulling it back and correcting the direction. Such blow excavation can also be carried out on the ground where excavation difficulty is low.

  By combining straight excavation and curved excavation as described above, ground excavation of an arbitrary route can be performed in one process as shown in FIG.

Inner tool recovery : After excavating the ground according to the target excavation route, the inner tool 7 is recovered from the outer tool 6. As described above, the recovery is performed by feeding the overshot 4 connected to the recovery rod 3 to the rod portion 2, connecting the overshot 4 to the spear 38, and pulling back the recovery rod 3.

Pipe laying : Once the inner tool 7 has been collected, the pipe is fed into the rod part 2 and the hollow outer tool 6 for laying. Then, the rod portion 2 and the outer tool 6 are pulled back and collected by the excavation propulsion device 5. In this way, various pipes such as a horizontal well pipe, a chemical solution injection pipe for recovering contaminated ground, a water and sewage pipe, a gas pipe, and a data receiving cable housing pipe can be laid on the ground.

Modification of the embodiment

  The cantilever excavator and the cantilever excavation method can be modified in various forms. An example is given below.

  About the said embodiment, it can comprise as a thing provided with the casing pipe | tube which attached the ring bit to the front-end | tip at the outer periphery of the rod part 2. FIG. That is, after excavating with the excavating tool 1, a casing pipe with a ring bit attached to the tip is single excavated from the starting side using the outer periphery of the rod part 2 as a guide and laid on the ground, and after the casing pipe is laid, excavated with the rod part 2 Tool 1 can be pulled back and collected. In this case, the casing tube itself may be used as it is as a tube used for the intended purpose, leaving the ground as it is. Or the pipe | tube used for the target application may be inserted in the pipe | tube of a casing pipe | tube, and you may make it pull back only a casing pipe | tube after insertion. The casing pipe can also be laid on the ground by alternately performing excavation by the excavation tool 1 and single excavation by the casing pipe with a predetermined excavation length.

  In the above-described embodiment, a water passage hole is formed in the rod part 2, and the rod part 2 can be used as a horizontal well pipe, a chemical solution injection pipe for recovering contaminated ground without being collected.

  In the above embodiment, one joint portion 22 is provided on the inner tool 7, but it may be provided at a plurality of locations.

  In the above embodiment, the spear 38 that is the rearmost part of the inner tool 7 is located in the pipe of the reducer 11 that is the rearmost part of the outer tool 6, but is substantially located in the pipe of the outer tool 6 (reducer 11). Alternatively, it may be configured to protrude to the rod portion 2.

  In the above embodiment, the recovery rod 3 is used, but instead, the wire line may be connected to the overshot 4. Further, instead of the recovery rod 3 and the overshot 4, a hollow or solid rod that can be directly connected to the spear 38 may be used. Further, the spear 38 may have a threaded portion instead of the engaging head 38a, and a rod or the like having a threaded portion connectable to the spear 38 may be used.

The internal structure sectional view of the excavation tool by the cantilever excavation device of one embodiment. Sectional drawing of an outer tool and a rod part. Sectional drawing of an inner tool. Operation | movement explanatory drawing of an inner tool. Explanatory drawing of connection operation of overshot and inner tool. Explanatory drawing of the one-way pushable excavation construction method by one Embodiment.

Explanation of symbols

1 Drilling tool
2 Rod part
3 Collection rod (Linear for collection)
4 Overshot (Linear for collection)
5 Drilling propulsion device
6 Outer tool
7 Inner tool
8 Outerbit
9 Coupling
10 Sonde Case
11 Reducer
12 super steel tip
13 Earth pressure receiving surface
14 Front engagement receiver
15 Engagement groove
16 Rear engagement receiver
17 Sonde
18 Transmission part
19 Passage
20 Innabit
21 Latch part (latch)
22 joints
23 Sonde storage
24 Earth pressure bearing surface
25 Engagement protrusion
26 Passage
27 Injection port
28 shaft
28a rear end
28b Guide inner surface
29 Engagement blade
29a shoulder
30 Rotating spindle
31 Spring
32 Actuating rod
32a Rear end
33 Latch case
33a Open edge
34 Spring
35 Rotating spindle
36 Innasonde Case
37 cushioning material
38 Spear
38a Engagement head
39 cases
39a Insertion hole
40 Latch piece
41 Rotating spindle
42 Extension rod

Claims (8)

A cylindrical rod portion connecting a plurality of extension rods;
A cylindrical outer tool that is connected to the tip of the rod part and has an outer bit attached to the tip for excavating the ground ;
An inner tool that is substantially housed in the outer tool so that it can be inserted into and removed from the outer tool and the rod part, and an inner bit is attached to the tip.
An engagement receiving portion is provided on the rear end side of the outer bit in the outer tool, and a latch that can be engaged with and disengaged from the engagement receiving portion is provided in the inner tool,
A continuous rotation or continuous rotation stop along the axis of the rod portion, and a striking or hitting stop along the axial direction of the rod portion, at least one of a propulsive force pushing piece with combination Lock only through de section the outer tool A one-sided excavation device that excavates the ground freely by transmitting and causing the one-side pushing propulsive force to act on the inner tool at the rear end side position of the outer bit by engaging the latch with the engagement receiving portion . The one-side pushable excavator according to claim 1, wherein the latch is provided on the rear side of the inner bit. The one-way pushable excavator according to claim 1 or 2 , further comprising a collection linear body that can be inserted into the rod portion and the outer tool and can be connected to the inner tool.   The one-side pushable excavation device according to any one of claims 1 to 3, wherein the inner tool is provided with a joint portion that is bent with respect to the axial direction thereof.   The one-side pushable excavator according to any one of claims 1 to 4, further comprising an excavation propulsion device that applies the one-side pushing propulsion force to the rod portion. An inner tool having an inner bit at the tip is accommodated inside an outer tool having an outer bit at the tip, and the engagement receiving portion provided on the inner tool at an engagement receiving portion provided on the rear end side of the outer bit of the outer tool. The inner tool is fixed inside the outer tool by engaging the detachable latch with the inner tool, and the outer tool penetrates into the ground together with the inner tool through the extension rod connected to the rear end of the outer tool. , outer via the stopping of the continuous rotation or the continuous rotation along the axis of the extension rod, stop the blow or the blow along the axial direction of the rod portion, only the extended length rod pieces pushing thrust with a combination of thereby transmitted to the tool, the driving force pushing the piece by the latch to the engagement receiving portion is engaged with the inner tool at the rear end position of Autabitto work Freely drilling method press pieces by freely excavate the ground.   7. After the excavation of the ground, the recovery linear body is inserted from the start side opening end of the extension rod and connected to the rear end of the inner tool, and the recovery linear body is pulled back to recover the inner tool. The one-sided free excavation method described.   8. The one-way push according to claim 7, wherein after the inner tool is collected, the pipe is laid on the ground by inserting a pipe from the opening side opening end of the extension rod, and then pulling back the extension rod and collecting the extension rod and the outer tool. Free excavation method.

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